This invention concerns the dimensional control of a material rolled in a continuous rolling machine having a grooved roll, for example, a bar steel mill or a wire mill.
An example of the structure of a continuous rolling machine of this type is shown in FIG. 1.
FIG. 1 shows a continuous rolling machine comprising i mill stands, wherein a first mill stand 1, a second mill stand 2, on i-1th mill stand 3, and ith mill stand 4, and a material 5 to be rolled are shown.
The successive rolling mill in FIG. 1 is a so-called VH type rolling mill. That is, horizontal mill stands (odd numbered stands in FIG. 1) and vertical mill stands (even numbered stands in FIG. 1) are arranged alternately.
For instance, the i-1th mill stand 3 is a vertical mill stand which performing rolling in the direction X. In FIG. 1, reference character bi-1 represents the lateral dimension and reference character hi-1 represents the vertical dimension at the exit of the i-1th mill stand 3. On the other hand, ith mill stand 4 is a horizontal mill stand which performs rolling in the direction Y. Reference character bi represents the lateral dimension and reference character hi represents the vertical dimension at the exit of the ith mill stand 4.
Conventional continuous rolling machines such as a bar steel mill and a wire mill employ a loop control and a tension control mechanism as a means for reducing the tension between the mill stands to zero. However, dynamic control has yet to be provided in the art because of the following reasons.
(1) There have been no severe requirements on the dimensions of the products. PA1 (2) Mill elongation due to a change in the load during rolling is small (which makes the dimensional accuracy of the products better since the effect of transferring the change at the inlet of the rolling material to the exit is decreased).
Accordingly, since no particular control has been exercised, in the conventional control system, over the change of dimensions relative to the change in the temperature of rolling material or the like, dimensional accuracy has been worsened.